Banded iron formation with ice-rafted debris. This deep ocean stratigraphic equivalent of Ghaub diamictites indicates highly anoxic oceanic chemistry. The grey is hematite, the red is jasper, and the buff is siderite.

The sample is from the Mackenzie Mountains in northwest Canada. Banded iron deposition requires that oceanic conditions be anoxic enough to allow for the precipitation of reduced iron (magnetite). Localized hematitic spotting is interpreted as the result of oxidation by dropstone deposition during the deep-freeze stage of a Snowball event. PFH-R is viewed as the stratigraphic equivalent of units like the Ghaub diamictite, but was deposited in a much deeeper oceanic basin during periods when ice cover prevented oceanic mixing and waters were highly anoxic.

Sample is 5.5 cm across at its widest point.

This sample is from the Snowball Earth Educational Rock Sample Suite, and comes courtesy of Paul Hoffman, Harvard University; Eugene Domack, Hamilton College; and Timothy Fox, Hamilton College.
For more information on the Snowball Earth Educational Rock Sample Suite, visit www.snowballearth.org/samples.html .
Image made as part of the MAGIC project (Mid-Atlantic Geo-Imagery Collection) using Northern Virginia Community College's gigamacro rig, as seen here:
gigamacro.com/gigapixel-macro-imaging-system /